1. Field of the invention
The present invention relates to a process for preparing a high .alpha.-glycosyl-L-ascorbic acid content product and separation system for said process, more particularly, to a process for preparing a high .alpha.-glycosyl-L-ascorbic acid content product from an aqueous solution containing .alpha.-glycosyl-L-ascorbic acid together with other concomitants such as L-ascorbic acid and a saccharide, and to a separation system for said process.
2. Description of the prior art
As disclosed in Japanese Patent Laid-Open Nos.135,992/91 and 139,288/91, .alpha.-glycosyl-L-ascorbic acid is a saccharide derivative of L-ascorbic acid which has the chemical structure as shown in Formula 1, and, unlike L-ascorbic acid, exhibits no direct reducing activity and has a satisfiable stability, as well as being readily hydrolyzed in vivo to exert the inherent activity of L-ascorbic acid. ##STR1##
As disclosed in Japanese Patent Laid-Open Nos.135,992/91 and 183,492/91, the preparation of .alpha.-glycosyl-L-ascorbic acid is effected by subjecting an aqueous solution containing L-ascorbic acid and an .alpha.-glucosyl saccharide to the action of a saccharide-transferring enzyme with or without glucoamylase.
The reaction mixture thus obtained contains a relatively-low amount of the .alpha.-glycosyl-L-ascorbic acid and relatively-large amounts of other concomitants such as L-ascorbic acid and saccharides.
In order to prepare a high .alpha.-glycosyl-L-ascorbic acid content product from the reaction mixture, adsorption and desorption using an anion-exchange resin is used, and column chromatography using a cation-exchange resin have been known.
The adsorption and desorption is a purification method which comprises demineralizing a reaction mixture with a cation-exchange resin (H.sup.+ -form), allowing the resultant demineralized solution to adsorb on an anion-exchange resin (OH.sup.- -form), washing the anion-exchange resin with water to remove saccharides such as D-glucose and .alpha.-glucosyl saccharide, and eluting the substances adsorbed on the anion-exchange resin with an acid- or salt-solution.
The method, however, has drawbacks in that it has a complicated step and requires relatively-large amounts of water, eluate and agent for regeneration; and that the concentration and the yield of the resultant .alpha.-glycosyl-L-ascorbic acid are relatively low.
It was found that column chromatography wherein a cation-exchange resin is used has a drawback in that it requires a relatively-large amount of water to effect separation of ingredients, and because of this the objective .alpha.-glycosyl-L-ascorbic acid solution is diluted and the production cost increases.
There has been a great demand to establish an industrial-scale preparation process for a high .alpha.-glycosyl-L-ascorbic acid content product from an aqueous solution containing .alpha.-glycosyl-L-ascorbic acid together with other concomitants such as L-ascorbic acid and saccharides.